The present invention relates to a tube for heat transfer systems or the like and, more particularly, to a tube having helically or circumferentially disposed, radially extending ribs or fins, wherein the base of the grooves between the fins has a plurality of discrete impressions defined therein.
Finned tubes for heat transfer systems are known, generally, as for example as shown in U.S. Pat. Nos. 3,791,003 and 3,893,322 and European Patent Application No. 0,102,407. In the latter publication, the internal face of the tube has an interrupted waviness corresponding to the grooves disposed between the fins. Further, individually separated projections of displaced tube material are provided on the interrupted waves. The internal surface of the tube so provided results in favorable heat transfer properties on the tube internal wall. The separate projections correspond to separate depressions formed in the groove of the tube outer wall which run in the direction of the groove. Though these depressions in the area of the groove base increase the surface area of the tube external surface, as compared with a non-formed tube, they exert only a limited influence on the heat transfer to the tube external face itself.
Accordingly, it would be desirable to provide a finned tube which advantageously influences the heat transfer to the tube external surface.